Prosthetic knee joint assembly with mutually slidable and rollable joint sections

ABSTRACT

An implantable prosthetic knee joint assembly has mutually rollable and slidable upper and lower joint sections. A single retainer pin in an oversize bore or a link and two retainer pins in oversize bores assist muscles and tissues to prevent separation of the joint sections after implantation in a leg. The retainer pins are not weight bearing during leg extension and leg flexure. One joint section has a resilient shock absorbing plastic bearing member. The bearing member of the other joint section may be made of metal. Both bearing members have contacting, smooth, substantially frictionless bearing surfaces. Sufficient free play is provided by the mountings of the retainer pins in oversize bores to permit the weight bearing members to contact each other rollably and slidably when the leg flexes and when it is extended. The joint sections have outwardly extending shanks adapted for securement in the thigh and calf of a person&#39;&#39;s leg. The bearing members are shaped so that articulation of the joint sections closely simulates human knee joint action.

United States Patent [191 Goldberg et al.

[451 Oct. 16, 1973 PROSTI-IETIC KNEE JOINT ASSEMBLY WITH MUTUALLYSLIDABLE AND ROLLABLE JOINT SECTIONS [76] Inventors: Donald D. Goldberg,184-52 Tudor Rd., Jamaica, N.Y. 11432; Stanley R. Rosen, Geraldine PL,Spring Valley, N.Y. 10977 [22] Filed: Jan. 19, 1971 21 Appl. No.:107,627

[52] US. Cl 3/1, 3/22, 3/27, 128/92 C [51] Int. Cl. A6lf 1/24, A61f1/04,A6lf1/08 [58] Field of Search 3/27, 22, 26, 2, 3/1', 128/92 C, 92 R [56]References Cited UNITED STATES PATENTS 3,506,982 4/1970 Steffee 3/13,694,821 10/1972 Moritz.... 128/92 C X 2,400,032 5/1946 Talbot 3/272,046,069 6/1936 Greissinger.... 3/29 3,638,243 2/1972 Campbell et al3/1 FOREIGN PATENTS OR APPLlCATIONS 1,122,634 5/1956 France 128/92 C163,476 6/1958 Sweden 128/92C 48,833 12/1953 Italy 3/27 1,047,640 7/1953France .1 128/92 c Primary Examiner-Richard A. Gaudet AssistantExaminer-Ronald L. Frinks Attorney-Jacob B. Burke [5 7] ABSTRACT Animplantable prosthetic knee joint assembly has mutually rollable andslidable upper and lower joint sections. A single retainer pin in anoversize bore or a link and two retainer pins in oversize bores assistmuscles and tissues to prevent separation of the joint sections afterimplantation in a leg. The retainer pins are not weight bearing duringleg extension and leg flexure. One joint section has a resilient shockabsorbing plastic bearing member. The bearing member of the other jointsection may be made of metal. Both bearing members have contacting,smooth, substantially frictionless bearing surfaces. Sufficient freeplay is provided by the mountings of the retainer pins in oversize boresto permit the weight bearing members to contact each other rollably andslidably when the leg flexes and when it is extended. The joint sectionshave outwardly extending shanks adapted for securement in the thigh andcalf of a persons leg. The bearing members are shaped so thatarticulation of the joint sections closely simulates human knee jointaction.

8 Claims, 22 Drawing Figures Patented Oct. 16,1973 3,765.033

4 Sheets-Sheet l INVENTORS. DONALD OLDBERG Y STANLEY ROSEN Uta/5%ATTORNEY Patented Oct. 16, 1973 3,765,033

4 Sheets-Sheet 2 FIG. I I. 2

INVENTORS. DONALD D. GOLDBERG STANLEY R. ROSEN ATTORNEY 4 Sheets-Sheet 598 EY 9O gill.

m -65a 32a 92 IHIIQ FIG.I8.

36a 54 56 5| INVENTORS DONALD D. GOLDBERG FIG. '7. BY STANLEY R. ROSENATTORNEY Patented Oct. 16, 1973 3,765.033

'4 Shooter-Sheet 4 5b132b R1 INVENTORS.

DONALD D. GOLDBERG STANLEY R. ROSEN EMMA ATTORNEY PROSTHETIC KNEE JOINTASSEMBLY WITH MUTUALLY SLIDABLE AND ROLLABLE JOINT SECTIONS Thisinvention concerns improved prosthetic knee joint assemblies primarilyintended to replace damaged human knee joints but also adaptable forinstallation in artificial legs.

Heretofore, prosthetic knee joints have been made of heavy metal partshaving two sections rotating on a fixed hinge pin. This hinge pin servesas a weight bearing axle during mutual rotation of the two jointsections. The hinge pin constrains the sections to rotate circularlyaround the pin. Such circular rotation does not conform to normal,natural knee flexing, which results in uncomfortable, stilted, hesitantwalking movements. When such a joint is flexed to its limits ofstraightening and bending and 90), the metal-tometal impact causesmechanical shocks which are painful to the person carrying theprosthetic joint. Furthermore the sounds of metal-to-metal impact aredisturbing and embarassing. To avoid such unpleasant shocks and noisesthe person tends to limit unduly the permissible range of motion of theknee joint. This again results in stilted, awkward walking movements,curtailment of normal leg movements and reduced bodily activities. Alsoobjectionable is the tendency of such repeated metal-to-metal impacts tocause loosening of the prosthetic anchoring shanks and posts in the legbones. The all'metal prior prosthetic knee joints also caused discomfortand fatigue to persons carrying them, due to their massive structure andheavy weight. Further difficulties arose from the fact that all weightwas concentrated on the hinge pins. This further increased discomfortand fatigue. Still further difficulties arose from the fact that therewas no way of lubricating the metal bearing parts. This caused prematurewear,

generated heat and friction, and strained the leg muscles with extrawork to force flexing of the joints. Some prior prosthetic joints have amaximum range of 90 of flexing which is very'limited to start with andis further reduced by the persons limitation of flexing to avoid shockimpact as above mentioned. Still other prior prosthetic joints displacedthe normal and natural position of the leg bones while bending. Thiscaused un'- comfortable, stilted, unnatural, hesitant walking movements.

The'present invention is directed at overcoming the above and otherdifficulties and disadvantages of prior prosthetic knee joints.According to the invention, a new prosthetic knee joint assembly can beconstructed in such away that the leg bones move in a natural,comfortable way while the knee is bending. The bones are not unnaturallydisplaced while the-joint is flexing. The new joint assembly is reducedmaterially in weight as compared with an all metal joint, by provisionof a plastic bearing member. The plastic member has a smooth, slippery,self lubricating surface which slides noiselessly and freely overadjacent metal parts. The plastic bearing member contacts adjacent metalparts almost shocklessly and noiselessly when the knee is straightenedand when it is fully flexed, due to the inherent resiliency of theplastic material. The tendency to loss of bond between anchoring partsof the prosthesis and leg bones due to metalto-metal impacts heretoforeencountered, is substantially eliminated.

According to the invention, bending of the joint is accomplished byrotating the upper ball joint section on a platform or track simulatingthe construction of human knee condyles. The joint sections are engagedby a retainer pin or pins set in an oversize bore or bores in bearingmembers and links. These pins serve only as retainer members to preventseparation of joint sections and are not load bearing when the leg bonesare weighted or loaded. Clearance is providedbetween the pins and theirretaining holes or bores so that outer surfaces of the plastic balljoint parts roll or slide in contact with lower bearing parts. This is aplastic-to-metal contact. It is stable, noiseless, and substantiallyfrictionless. Contact is maintained continuously between the plastic andmetal parts at all times when the joint is weight or load bearing bothwhen flexing and when stationary in flexed or straightened position. Atother times when the joint is not weight bearing the bearing parts areslightly separated and held in place by muscles and tissues and bones inthe thigh and calf ofthe leg assisted by the retaining pin. Thiscontrasts with prior prosthetic joints where hinge or pivotpins serve asload bearing axles at all times. If these axles were postoperativelyremoved, the joints could not flex or operate. By the presentarrangement, the thigh and calf to whichthe knee joint sections arerespectively at tached each turn on a radius several timeslarger than ispossible with conventional prosthetic knee joints rotating on hinge pinswhich are weight bearing axles at all times. The arrangement of thepresent invention more closely simulates the structure and actualoperation of human knee joints. Due to the larger rotational radius, thebearing area under load isincreased and pressure at each bearing pointis consequently reduced. As a result, the parts roll and slide easierand more comfortably. Wear of bearing parts is substantially eliminated.The new construction makes it possible to provide an extended range offlexing up to 150 which is more than percent greater than has heretoforebeen obtainable in prior knee joints. In addition there is eliminatedthe prior tendency of patients to limit the rangeof knee flexing, byeliminating the shocks received from prior metal-to-metal knee jointimpacts.

The invention further provides means for providing a range and characterof motion of legcomponents adapted to the condition of their-legmuscles. Younger persons having more resilient leg muscles can beprovided with prosthetic knee joints having a greater range of motionthan is provided older persons having less resilient muscIesQThe newprosthetic joints are provided with shanks or posts shaped so that bonegrowth will tend to secure them from relative 'motion in their anchoringleg bones. Theshanks or posts can be secured ,in place in the femur andtibia by suitable' surgical cement.

Other and further features, objects and advantages of the invention willbecome apparent from the following detailed description taken togetherwith the drawings, wherein:

FIG. 1 is a perspective view showing top, front and one side of aprosthetic knee joint assembly embodying the invention, with parts inunflexed open position.

FIG. 2 is a perspective view of the joint assembly similar to FIG. 1,but showing the top, rear and opposite side of the assembly.

FIG. 3 is a front elevational view of the unflexed joint assembly.

FIG. 4 is an enlarged fragmentary side view of the joint assembly inflexed position.

FIG. 5 is an enlarged fragmentary vertical sectional view taken on lines5-5 of FIG. 3.

FIG. 6 is another enlarged fragmentary vertical sectional view taken online 66'of FIG. 3.

FIG. 7 is a horizontal cross sectional view taken on line 7-7 of FIG. 6.

FIG. 8 is an exploded perspective view of parts of the prosthetic kneejoint of FIGS. 1-7.

FIG. 9 is a perspective view similar to FIG. 1 showing top, front andone side of a second prosthetic knee joint in unflexed position.

FIG. 10 is a perspective view similar to FIG. 2 show- 7 ing top, rearand opposite side of the second knee joint assembly of FIG. 9.

FIG. 11 is a fragmentary enlarged front elevational view of the secondknee joint assembly.

FIG. 12 is a fragmentary enlarged rear elevational view of the secondknee joint assembly.

FIG. 13 is a fragmentary side elevational view taken on line 13 13 ofFIG. 11.

FIG. 14 is a side view similar to FIG. 13 showing the joint assembly inpartially flexed position.

FIG. 15 is a view similar to FIG. 14 showing the joint assembly in fullyflexed position.

FIG. 16 is a reduced vertical sectional view taken on line 16-16 of FIG.12.

FIG. 17 and FIG. 18 are horizontal sectional views taken on lines 17-17and 18-18 respectively of FIG. 16.

FIG. 19 is an exploded perspective view of parts of the second kneejoint assembly shown in FIGS. 9-18.

FIG. 20 is a fragmentary side elevational view similar to FIG. 13showing'a third prosthetic knee joint assembly embodying the invention,in unflexed open position.

FIG. 21 is a vertical sectional view of the third knee joint assembly inunflexed open position.

FIG. 22 is a side elevational view similar to FIG. 20 but showing thethird knee joint assembly in flexed position.

Referring first to FIGS. 1-8, there is shown a prosthetic knee jointassembly .11 having an upper condylar section 25 and a lower condylarsection 30. The upper section comprises a bearing member 32 made ofstrong, dimensionally and chemically stable plastic material. Thebearing member has two laterally spaced integral cylindrical rollerbearing parts 34,36. External surfaces 38 of these parts are smooth andslippery so that the joint is in effect self lubricated and requires nofurther lubrication. The bearing member 32 has a flat top on which seatsa metal mounting plate 40. The plate carries an upright metal shank orpost 42 secured thereto. The shank is adapted for-insertion in the femurof a leg in which the joint is to be installed. Plate 40 is held inplace by locating pins 43 and a screw 46. The locating pins are insertedin holes 44,45 in plate 40 and the top of bearing member 32. Screw 46has a head 47 seated in recess 48 in member 32 and its shank is screwedinto plate 40 and post 42; see FIG.5. Post 42 is tapered and disposed atan angle of 7 to the right or left of the vertical axis of the assemblyas viewed from the front, depending on whether the joint assembly is tobe installed in a persons right leg or left leg respectively; see FIG.3. The shank 42 may be formed with circumferentially spaced longitudinalgrooves 49 which receive bone growth to help secure the post in place inthe thigh where it is installed. The shank can further be secured inplace with a suitable surgical cement to prevent dislocation of thejoint assembly with respect to the leg in which it is installed.

Bearing member 32 is further formed with axially aligned bores 50, 52extending centrally through the cylindrical bearing parts 34, 36. End 51of bore 50 is enlarged to receive head 54 of a retainer pin 56. The headhas a recess for engagement by a suitable wrench. End 53 of bore 52 isenlarged to receive a flattened nut 58 in which the threaded end 59 ofpin 56 is screwed. It will be noted that bores 50,52 and their ends 51,53 are all larger in width or diameter than the width or diameter of thepin and nut at all points. The purpose of this arrangement is describedfurther below. The center portion 57 of pin 56 is slightly larger indiameter than adjacent portions 60, 62 which are disposed in bores 50,52 respectively. The center portion 57 of the pin extends through a bore64 formed in upwardly projecting head 66 of lower condylar section 30.The diameter of center portion 57 is slightly smaller than that of bore64.

The lower condylar section 30 includes a bearing and hinge member 65formed with two laterally extending portions 68 having uppercylindrically curved surfaces 70 defining bearing seats for thecylindrically curved surfaces 38 of roller bearing parts 34, 36.

A tapered shank or post 72 similar to post 42 is secured to the base ofsection 30 and depends therefrom. This shank is formed with.longitudinally extending grooves 74 to receive bone growth and to helpin anchoring the shank in a leg. The shank is adapted for securement bya surgical cement in the tibia of the leg where the joint assembly isinstalled.

When the joint assembly is installed and cemented in place in the thighand calf of a leg, the surgeon will arrange muscles of the leg in frontof the joint sections 25, 30 to effect flexing of the leg and thus serveas hinge means for the knee joint. Flexing will occur in a mannerillustrated by FIG. 4. Pin 56 serves as a connector to preventseparation of the joint parts. The looseness of. the pin inoversize'bore 52 permits free flexing of the joint sections through anangle of as much as 150 when the leg is flexed. The leg will be weightbearing when a person is standing, walking or in the acts of sittingdown or standing up. At such times there will be direct continuouscontact between-the joint sections 25,30. Pin 56 will not bear anyweight. Surfaces 38 and 70 will then be in continuous sliding androlling contact through the entire range of motion of the joint sectionsbetween the upright, extended unflexed position of FIG. 6 and the fullyflexed or bent position.- When the joint is fully opened andstraightened, flat fact75 of head 66 abuts the rear flat side 76 ofmember 32 between bearing parts 34, 36. When the joint assembly is notloaded as occurs during walking and while lying down a slight space Sthen exists between bearing surfaces 38 and 70 as shown in FIG. 4. Thelower tibial section 30 then swings freely supported bymuscles of thetibia. The natural flexibility in the muscles of the leg permits thisslight relative, longitudinal, self positioning of the joint sections.The amount by which the bores are oversize with respect to the width ofpin 56 and nut 58 at all points determines the relative longitudinalmovement of sections 25, 30. It should be emphasized at this point, thatpin 56 floats free. It is essentially unloaded and non-load bearingwhile the joint assembly itself is load bearing. The pin then servesonly as an auxiliary retainer means to prevent separation of the jointsections. When the joint assembly is not loaded or weighted the pinfloats free. The surfaces 38 and 70 may be but need not necessarily bein sliding contact with each other. It will be noted that in the fullyextended position of the joint sections, face 75 of head 66 abuts flatside 76 of member 32. In fully rotated or flexed position of the jointsections as shown in FIG. 4, side 76 of member 32 contacts face 77 ofhead 66. By this arrangement substantially shockless plastic-tometalcontact of the parts occurs when the joint is fully open and closed. Themetal parts of the joint assembly are preferably made of stainless steelbut they can be made of other noncorrosive, strong, lightweight metal.The muscles tissues which restrain and control articulation of the jointsections are indicated by dotted lines in FIGS. 4 and 5.

Joint assembly Jl will in general be used for older persons or personsrequiring a simple rotary motion at the knee. For younger persons havingmore resilient leg muscles and requiring a wider range of motion, jointassembly J2 shown in FIGS. 9-19 may be provided. Parts of joint assemblyJ2 corresponding to those of assembly J1 are identically numbered.

In joint assembly J2, bearingand joint member 65a of lower condylarsection 30a is formed with a notch 80 in which a link 82 is pivotallyengaged byretainer pin 560. This pin has central, wider portion 57aengaged in oversized bore or hole 84 in the link. This hole is larger indiameter than that of pin portion 57; see FIGS. 16, 18. Pin portions 60a'and 62a are engaged in bores 86,88 formed in laterally spacedbearingportions 90,92 of bearing member 65a. Bores 86, 88 are larger indiameter than pin portions 60a,62a which they contain. Head 52a of pin56a'is seated in overside bore end 91. Flat nut 94 engages the threadedend 59a of the pin in bore end 93.Shank or post 72 is secured to anddepends from bearing member 65a. Two adjacent curved faces 96 and 98having different circumferential length but the same radius of curvatureare formed on top of each bearing portion 90, 92.

.Plastic bearing member 32a. of upper joint section 25a rotates androlls on-bearing faces 96, 98 when the joint is weight bearing. Pin 56serves to prevent separation of link 82 and bearing member 32a and doesnot serve as a weight bearing axle. The center pin section 57 isengagedin oversize hole 99 in link 82; see FIGS. 16 and 17. Pin portions 60 and62 adjacent the center section 57 are engaged in oversize bores 50, 52formed in the spaced, cylindrical rollling and sliding bearing parts340, 36a of bearing member 32a. Plate 40a earring upper shank-42 issecured to the top of bearing member 32a by pins 43 and screws 100.

By the structural arrangement described, bearing member 32a willnormally be spaced slightly by space S when the joint assembly isunloaded; see FIG. 13. This space is maintained by muscles and tissuesof the leg. When the upper and lower joint sections rotate with respectto each other under load, cylindrical surfaces 38 of the plastic bearingmember 32a will rotate and roll on concave faces 96 of largercircumferential length for about 90 while link 82 remains stationary;see FIG. 14. Then the upper joint section will rotate with link 82 intosliding engagement with concave bearing faces 98 and then the upperbearing member will continue to rotate further on faces 98 while link 82again remains stationary. This condition obtains for flexing in therange of to 150; see FIG. 15. In upright position of the joint assemblylink 82 contacts inner side 102 of notch 80 between bearing parts 34aand 36a. In the fully rotated position of the link, it contacts upperside 106 of notch 104. This metal-to-plastic sections closelyapproximates the condylar action occurring in a human knee. Parts ofassembly J3 corresponding to joint assemblies J1 and J2 are identicallynumbered. In joint assembly J3, upper joint section 25b is provided witha plastic bearing member 32b having a notch 104' centrally formedtherein between spaced lateral parts 34b and 36b of the bearing member.Link 82 in notch 104' is pivotally engaged by upper retainer pin 56 andis engaged in notch 80 of lower bearing member 65b by retainer pin 56a,as in joint J2. Both retainer pins are engaged in oversize bores in thebearing members and oversize holes in link 82 asin joint assembly J2.The faces 38" of lateral parts 34b and 36b progressively change andincrease in radius of curvature from smaller radius R2 to larger radiusR1. When the joint sections are in open upright position and under load,as shown in FIGS. 20,21, faces 38' of bearing member 32b bear on theupper face'96' of bearing member 65b. Face 96' can be flat or curved.Link 82 then assumes a maximum angle of inclination and may contactinner side 80" of notch 80' and inner side 102' of notch 104'. This is aposition of stability with joint fully open. Upper section 25b can turncounterclockwise as viewed in FIGS. 20 and 21 to the lowered, closedstable position shown in FIG. 22 when front side of bearing member 32brests on theupper face 'of bearing member-65b. As link 82' turns to theleft, the distance it protrudes above face 96' at any point will alwaysbe such that faces 38 always remain in contact with face 96'. Since thisdistance changes and increases continuously, the radius of faces 38'increases progressively frorn radius R2 to radius R1.- This cam-likeaction simulates very closely the condylara'ctionoccurring in the humanknee. The muscles M which restrain and control the articulation of thejoint sections are indicated by dotted lines in FIGS.'20- 22.-

It will be apparent from the foregoing that there has been provided avariety of pr'osthetickneejoint structures adapted to different patientsrequirements. In all knee joint assemblies there are employedplastic-tometal rolling and'sliding contacts of bearing parts. In allknee joint assemblies the retainer pins in oversize bores serve only asretainer means to assist muscles and tissues of the leg in preventingseparation of joint parts, and are not weight bearing axles. Weightbearing while the knee joint isstraightened, flexed or flexing isaccomplished by continuous plastic-to-metal contacts of Y the bearingparts. At other times clearance is maintained between the plastic andmetal bearing parts by muscles and tissues of the leg. While a limitednumber of embodiments of the invention have been described in detail itwill be understood that this has been only. by way of example. It willbe apparent that many modifications and variations are possible withoutdeparting from the invention. Among the variations possible isconstruction of knee joint assemblies having both bearing members madeof plastic, or both members made of metal, or either one of plastic andthe other one of metal. It is also possible to adapt the knee jointassemblies for incorporation in artificial legs. Still othermodifications, variations and applications of the invention may bepossible without departing from the invention as claimed.

What is claimed is:

1. A prosthetic knee joint assembly, comprising mutually rollable andslidable upper and lower joint sections mountable to the thigh and calfrespectively of a human leg, the upper joint section comprising a firstweight bearing member having a lower first bearing portion, the lowerjoint section having an upper second bearing portion, both jointsections having attachment structure means adapted for securement of thejoint sections to thigh and calf bones respectively of the leg, bothbearing portions having mutually contacting, smooth, substantiallyfrictionless surfaces so that the joint sections rollably and slidablycontact each other when under the influence of body weight and whileflexing; and transverse retainer means in both joint sections to preventseparation of the joint sections while permitting free relative motionthereof, said joint sections having transverse bores receiving saidretainer means so that the latter floats free and is free of load whenthe bearing surfaces of the joint sections are in contact with eachother under the influence of body weight.

2. A prosthetic knee joint assembly as defined in claim 1, wherein atleast one of the bearing portions is composed of a plastic materialhaving a smooth, slippery bearing surface to minimize friction betweenthe bearing members when in sliding contact with each other, saidplastic material having sufficient resiliency to prevent substantiallyoccurrence of mechanical shocks and impact noises between the jointsections when the joint sections are fully opened and closed.

3. A prosthetic joint assembly as defined in claim 1, wherein the firstbearing portion is composed of the plastic material which is resilientenough to absorb mechanical shocks so that the legextends and flexesshocklessly at the contacting joint sections, the second bearing portionbeing composed of a rigid material so that the upper joint section rollsand slides silently,

smoothly, freely and easily with respect to the lower joint section.

4. A prosthetic joint assembly as defined in claim 1, wherein saidretainer means comprises a generally cylindrical retainer pin havingdifferent diameters at different points, said pin extending through thebores in both joint sections, said bores having diameters larger thanthe diameters of adjacent points of the pin at all points in the boresto provide free lateralplay between the joint sections, and to permitboth flexure and extension of the joint sections.

5. A prosthetic knee joint assembly as defined in claim 4, wherein atleast one of the bearing portions is composed of a plastic materialhaving a smooth, slippery bearing surface to minimize friction betweenthe bearing members when in sliding contact with each other, saidplastic material having sufficient resiliency to prevent substantiallyoccurrence of mechanical shocks and impact noises between the jointsections when the joint sections are fully opened and closed.

6. A prosthetic joint assembly as defined in claim 1, wherein saidretainer means comprises a link and two generally cylindrical retainerpins having portions of different diameters, said link having spacedholes respectively aligned with the bore in the joint sections, said,retainer pins respectively extending through the holes and bores in thelink and joint sections, said holes and bores having diameters largerthan the diameters of all adjacent portions of the retainer pins in theholes and bores to provide free lateral play of the pins between thejoint sections and to permit flexure and extension of the jointsections.

7. A prosthetic knee joint assembly as defined in claim 6, wherein atleast one of the bearing portions is composed of a plastic materialhaving a smooth, slippery bearing surface to minimize friction betweenthe bearing members when in sliding contact with each other, saidplastic material having sufficient resiliency to prevent substantiallyoccurrence of mechanical shocks and impact noises between the jointsections when the joint sections are fully opened and closed.

8. A prosthetic knee joint assembly as defined in claim 1, wherein thebearing portion of one bearing member is cylindrically curved atleast'in part sothat the 1 joint sections flex with an angular motionsimulating human condylar knee action.

l l l IF

1. A prosthetic knee joint assembly, comprising mutually rollable andslidable upper and lower joint sections mountable to the thigh and calfrespectively of a human leg, the upper joint section comprising a firstweight bearing member having a lower first bearing portion, the lowerjoint section having an upPer second bearing portion, both jointsections having attachment structure means adapted for securement of thejoint sections to thigh and calf bones respectively of the leg, bothbearing portions having mutually contacting, smooth, substantiallyfrictionless surfaces so that the joint sections rollably and slidablycontact each other when under the influence of body weight and whileflexing; and transverse retainer means in both joint sections to preventseparation of the joint sections while permitting free relative motionthereof, said joint sections having transverse bores receiving saidretainer means so that the latter floats free and is free of load whenthe bearing surfaces of the joint sections are in contact with eachother under the influence of body weight.
 2. A prosthetic knee jointassembly as defined in claim 1, wherein at least one of the bearingportions is composed of a plastic material having a smooth, slipperybearing surface to minimize friction between the bearing members when insliding contact with each other, said plastic material having sufficientresiliency to prevent substantially occurrence of mechanical shocks andimpact noises between the joint sections when the joint sections arefully opened and closed.
 3. A prosthetic joint assembly as defined inclaim 1, wherein the first bearing portion is composed of the plasticmaterial which is resilient enough to absorb mechanical shocks so thatthe leg extends and flexes shocklessly at the contacting joint sections,the second bearing portion being composed of a rigid material so thatthe upper joint section rolls and slides silently, smoothly, freely andeasily with respect to the lower joint section.
 4. A prosthetic jointassembly as defined in claim 1, wherein said retainer means comprises agenerally cylindrical retainer pin having different diameters atdifferent points, said pin extending through the bores in both jointsections, said bores having diameters larger than the diameters ofadjacent points of the pin at all points in the bores to provide freelateralplay between the joint sections, and to permit both flexure andextension of the joint sections.
 5. A prosthetic knee joint assembly asdefined in claim 4, wherein at least one of the bearing portions iscomposed of a plastic material having a smooth, slippery bearing surfaceto minimize friction between the bearing members when in sliding contactwith each other, said plastic material having sufficient resiliency toprevent substantially occurrence of mechanical shocks and impact noisesbetween the joint sections when the joint sections are fully opened andclosed.
 6. A prosthetic joint assembly as defined in claim 1, whereinsaid retainer means comprises a link and two generally cylindricalretainer pins having portions of different diameters, said link havingspaced holes respectively aligned with the bores in the joint sections,said retainer pins respectively extending through the holes and bores inthe link and joint sections, said holes and bores having diameterslarger than the diameters of all adjacent portions of the retainer pinsin the holes and bores to provide free lateral play of the pins betweenthe joint sections and to permit flexure and extension of the jointsections.
 7. A prosthetic knee joint assembly as defined in claim 6,wherein at least one of the bearing portions is composed of a plasticmaterial having a smooth, slippery bearing surface to minimize frictionbetween the bearing members when in sliding contact with each other,said plastic material having sufficient resiliency to preventsubstantially occurrence of mechanical shocks and impact noises betweenthe joint sections when the joint sections are fully opened and closed.8. A prosthetic knee joint assembly as defined in claim 1, wherein thebearing portion of one bearing member is cylindrically curved at leastin part so that the joint sections flex with an angular motionsimulating human condylar knee action.